Adding Auth0.AuthenticationApi package dependency

EXAMPLES.md

@@ -444,3 +444,97 @@ public class LogoutModel : PageModel
     }
 }
 ```
+
+# Accessing Auth0.AuthenticationApi features
+`Auth0.AuthenticationApi` package is our standalone Authentication package that supports a wide range of
+options for Authentication. We can access these features like below : 
+
+```csharp
+/// Register the dependency in the container as below. 
+/// Program.cs / Startup.cs
+builder.Services.AddAuth0WebAppAuthentication(options =>
+{
+    options.Domain = "domain";
+    options.ClientId = "ClientId";
+    options.ClientSecret = "clientSecret";
+}).WithAuthenticationApiClient(); 
+
+
+/// Accessing the Api Client in the controller
+public AccountController(IAuthenticationApiClient apiClient)
+{
+    _apiClient = apiClient;
+}
+
+[Authorize]
+public async Task LoginWithAuthenticationApi()
+{
+    await _apiClient.GetTokenAsync(new ClientCredentialsTokenRequest()
+    {
+        ClientId = "",
+        ClientSecret = ""
+    }, new CancellationToken());
+}
+```
+
+# Accessing specific features like CIBA
+Although `Auth0.AuthenticationApi` package has a wide range of options for Authentication.
+We can access the CIBA feature as below. It aims to make it easy to integrate into an appllication.
+
+```csharp
+/// Register the dependency in the container as below. 
+/// Program.cs / Startup.cs
+builder.Services.AddAuth0WebAppAuthentication(options =>
+{
+    options.Domain = "domain";
+    options.ClientId = "ClientId"; // required
+    options.ClientSecret = "clientSecret"; // required
+}).WithClientInitiatedBackchannelAuthentication();
+
+
+/// Accessing the Auth0CibaService in the controller
+public AccountController(IAuth0CibaService auth0CibaService)
+{
+    _auth0CibaService = auth0CibaService;
+}
+
+public async Task<IActionResult> InitiateLoginWithCiba(string returnUrl = "/")
+{
+    var response = await _auth0CibaService.InitiateAuthenticationAsync(new CibaInitiationRequest()
+    {
+        Scope = "openid profile",
+        BindingMessage = "BindingMessage",
+        LoginHint = new LoginHint()
+        {
+            Format = "iss_sub",
+            Issuer = "https://dx-sdks-testing.us.auth0.com/",
+            Subject = "userId"
+        }
+    });
+
+    // Cache the details for polling.
+    TempData["AuthRequestId"] = response.AuthRequestId;
+    TempData["CibaInitiationDetails"] = JsonSerializer.Serialize(response);
+    return RedirectToAction("Waiting");
+}
+
+// You could use the built-in polling mechanism or could implement your own polling mechanism by 
+// accessing the `GetTokenAsync` method using the AuthenticationApiClient as shown in the example before.
+[HttpGet]
+public async Task<IActionResult> CheckCibaStatus()
+{
+    var cibaInitiateResponse = JsonSerializer.Deserialize<CibaInitiationDetails>(TempData["CibaInitiationDetails"]?.ToString() ?? string.Empty);
+    var authRequestId = cibaInitiateResponse?.AuthRequestId;
+    if (string.IsNullOrEmpty(authRequestId))
+    {
+        return Json(new { isError = true });
+    }
+
+    var status = await _auth0CibaService.PollForTokensAsync(cibaInitiateResponse);
+
+    if (status.IsSuccessful)
+    {
+        // Parse the accessToken / IdToken and use it as required.
+    }
+}
+```

src/Auth0.AspNetCore.Authentication/Auth0.AspNetCore.Authentication.csproj

@@ -5,6 +5,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Auth0.AuthenticationApi" Version="7.*" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="6.0.*" Condition="'$(TargetFramework)' == 'net6.0'" />
     <PackageReference Include="Microsoft.IdentityModel.Protocols.OpenIdConnect" Version="6.*" Condition="'$(TargetFramework)' == 'net6.0'" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="7.0.*" Condition="'$(TargetFramework)' == 'net7.0'" />

src/Auth0.AspNetCore.Authentication/Auth0WebAppAuthenticationBuilder.cs

@@ -5,6 +5,9 @@
 using System;
 using System.Threading.Tasks;
 using Auth0.AspNetCore.Authentication.BackchannelLogout;
+using Auth0.AspNetCore.Authentication.ClientInitiatedBackChannelAuthentication;
+using Auth0.AuthenticationApi;
+using Microsoft.Extensions.DependencyInjection.Extensions;
 
 namespace Auth0.AspNetCore.Authentication
 {
@@ -61,6 +64,31 @@ public Auth0WebAppAuthenticationBuilder WithBackchannelLogout()
             return this;
         }
 
+        /// <summary>
+        /// Configures the IAuthenticationApiClient to leverage Auth0.AuthenticationApi 
+        /// </summary>
+        /// <returns></returns>
+        public Auth0WebAppAuthenticationBuilder WithAuthenticationApiClient()
+        {
+            _services.AddSingleton<IAuthenticationApiClient>(
+                _ => new AuthenticationApiClient(new Uri($"https://{_options.Domain}")));
+            _services.AddTransient<ILogoutTokenHandler, DefaultLogoutTokenHandler>();
+            return this;
+        }
+
+        /// <summary>
+        /// Configures the IAuth0CibaService to leverage the CIBA features. 
+        /// </summary>
+        /// <returns></returns>
+        public Auth0WebAppAuthenticationBuilder WithClientInitiatedBackchannelAuthentication()
+        {
+            _services.TryAddSingleton<IAuthenticationApiClient>(
+                _ => new AuthenticationApiClient(new Uri($"https://{_options.Domain}")));
+            _services.TryAddScoped<IAuth0CibaService, Auth0CibaService>();
+
+            return this;
+        }
+
         private void EnableWithAccessToken(Action<Auth0WebAppWithAccessTokenOptions> configureOptions)
         {
             var auth0WithAccessTokensOptions = new Auth0WebAppWithAccessTokenOptions();

src/Auth0.AspNetCore.Authentication/ClientInitiatedBackChannelAuthentication/Auth0CibaService.cs

@@ -0,0 +1,131 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+
+using Auth0.AuthenticationApi;
+using Auth0.AuthenticationApi.Models.Ciba;
+using Auth0.Core.Exceptions;
+
+namespace Auth0.AspNetCore.Authentication.ClientInitiatedBackChannelAuthentication;
+
+internal class Auth0CibaService : IAuth0CibaService
+{
+    private readonly IAuthenticationApiClient _authenticationApiClient;
+    private readonly Auth0WebAppOptions _options;
+    private readonly ILogger<Auth0CibaService> _logger;
+
+    /// <summary>
+    /// Initiates an instance of Auth0CibaService which can be used to execute the CIBA workflow.
+    /// </summary>
+    /// <param name="authenticationApiClient">Instance of <see cref="Auth0.AuthenticationApi.IAuthenticationApiClient"/> </param>
+    /// <param name="optionsAccessor"><see cref="Auth0WebAppOptions"/></param>
+    /// <param name="logger"></param>
+    public Auth0CibaService(
+        IAuthenticationApiClient authenticationApiClient,
+        IOptions<Auth0WebAppOptions> optionsAccessor,
+        ILogger<Auth0CibaService> logger)
+    {
+        _authenticationApiClient = authenticationApiClient;
+        _options = optionsAccessor.Value;
+        _logger = logger;
+    }
+
+    /// <inheritdoc cref="Auth0.AspNetCore.Authentication.ClientInitiatedBackChannelAuthentication.IAuth0CibaService.InitiateAuthenticationAsync"/>
+    public async Task<CibaInitiationDetails> InitiateAuthenticationAsync(
+        CibaInitiationRequest request)
+    {
+        try
+        {
+            var cibaRequest = new ClientInitiatedBackchannelAuthorizationRequest
+            {
+                ClientId = _options.ClientId,
+                ClientSecret = _options.ClientSecret,
+                ClientAssertionSecurityKey = _options.ClientAssertionSecurityKey,
+                ClientAssertionSecurityKeyAlgorithm = _options.ClientAssertionSecurityKeyAlgorithm,
+                Audience = request.Audience,
+                LoginHint = request.LoginHint,
+                Scope = request.Scope,
+                RequestExpiry = request.RequestExpiry,
+                AdditionalProperties = request.AdditionalProperties,
+                BindingMessage = request.BindingMessage,
+            };
+
+            _logger.LogInformation("Initiating CIBA request!");
+            var response = await _authenticationApiClient.ClientInitiatedBackchannelAuthorization(cibaRequest);
+
+            return new CibaInitiationDetails()
+            {
+                AuthRequestId = response.AuthRequestId,
+                ExpiresIn = response.ExpiresIn,
+                Interval = response.Interval,
+                IsSuccessful = true,
+                ErrorMessage = null
+            };
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error initiating CIBA request");
+            throw;
+        }
+    }
+
+    /// <inheritdoc cref="Auth0.AspNetCore.Authentication.ClientInitiatedBackChannelAuthentication.IAuth0CibaService.PollForTokensAsync"/>
+    public async Task<CibaCompletionDetails> PollForTokensAsync(
+        CibaInitiationDetails initDetails, CancellationToken cancellationToken)
+    {
+        var request = new ClientInitiatedBackchannelAuthorizationTokenRequest()
+        {
+            ClientId = _options.ClientId,
+            ClientSecret = _options.ClientSecret,
+            ClientAssertionSecurityKey = _options.ClientAssertionSecurityKey,
+            ClientAssertionSecurityKeyAlgorithm = _options.ClientAssertionSecurityKeyAlgorithm,
+            AuthRequestId = initDetails.AuthRequestId
+        };
+
+        var completionDetails = new CibaCompletionDetails()
+        {
+            IsSuccessful = false,
+            IsAuthenticationPending = true
+        };
+
+        while (completionDetails is { IsAuthenticationPending: true, IsSuccessful: false })
+        {
+            _logger.LogDebug($"Polling CIBA token endpoint for auth_req_id: {initDetails.AuthRequestId} ");
+            try
+            {
+                var response = await _authenticationApiClient.GetTokenAsync(request, cancellationToken);
+
+                completionDetails.AccessToken = response.AccessToken;
+                completionDetails.IdToken = response.IdToken;
+                completionDetails.TokenType = response.TokenType;
+                completionDetails.Scope = response.Scope;
+                completionDetails.ExpiresIn = response.ExpiresIn;
+                completionDetails.RefreshToken = response.RefreshToken;
+                completionDetails.IsSuccessful = true;
+                completionDetails.IsAuthenticationPending = false;
+            }
+            catch (ErrorApiException ex)
+            {
+                _logger.LogWarning(
+                    ex,
+                    $"CIBA polling error for auth_req_id: {initDetails.AuthRequestId}." +
+                    $" Error: {ex.ApiError.Error}, Description: {ex.ApiError.Message}");
+
+                if (ex.ApiError.Error.Contains("authorization_pending", StringComparison.OrdinalIgnoreCase))
+                {
+                    await Task.Delay(TimeSpan.FromSeconds(initDetails.Interval));
+                    continue;
+                }
+
+                completionDetails.IsAuthenticationPending = false;
+                completionDetails.Error = ex.ApiError.Error;
+                completionDetails.ErrorMessage = ex.ApiError.Message;
+                completionDetails.IsSuccessful = false;
+            }
+        }
+        return completionDetails;
+    }
+}

src/Auth0.AspNetCore.Authentication/ClientInitiatedBackChannelAuthentication/IAuth0CibaService.cs

@@ -0,0 +1,81 @@
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Auth0.AuthenticationApi.Models.Ciba;
+
+namespace Auth0.AspNetCore.Authentication.ClientInitiatedBackChannelAuthentication;
+
+public class CibaInitiationDetails : ClientInitiatedBackchannelAuthorizationResponse
+{
+    /// <summary>
+    /// Indicates whether the polling was successful.
+    /// </summary>
+    public bool IsSuccessful { get; init; } = true;
+
+    /// <summary>
+    /// Indicates any errors that occurred during the initiation of the CIBA request.
+    /// </summary>
+    public string? ErrorMessage { get; init; }
+}
+
+public class CibaInitiationRequest
+{
+    /// <inheritdoc cref="Auth0.AuthenticationApi.Models.Ciba.ClientInitiatedBackchannelAuthorizationRequest.BindingMessage"/>
+    public string? BindingMessage { get; set; }
+
+    /// <inheritdoc cref="Auth0.AuthenticationApi.Models.Ciba.LoginHint"/>
+    public LoginHint? LoginHint { get; set; }
+
+    /// <inheritdoc cref="Auth0.AuthenticationApi.Models.Ciba.ClientInitiatedBackchannelAuthorizationRequest.Scope"/>
+    public string? Scope { get; set; }
+
+    /// <inheritdoc cref="Auth0.AuthenticationApi.Models.Ciba.ClientInitiatedBackchannelAuthorizationRequest.Audience"/>
+    public string? Audience { get; set; }
+
+    /// <inheritdoc cref="Auth0.AuthenticationApi.Models.Ciba.ClientInitiatedBackchannelAuthorizationRequest.RequestExpiry"/>
+    public int? RequestExpiry { get; set; }
+
+    /// <inheritdoc cref="Auth0.AuthenticationApi.Models.Ciba.ClientInitiatedBackchannelAuthorizationRequest.AdditionalProperties"/>
+    public IDictionary<string, string> AdditionalProperties { get; set; } = new Dictionary<string, string>();
+}
+
+public class CibaCompletionDetails : ClientInitiatedBackchannelAuthorizationTokenResponse
+{
+    /// <summary>
+    /// Signifies if the authentication is pending.
+    /// </summary>
+    public bool IsAuthenticationPending { get; set; } = true;
+
+    /// <summary>
+    /// Signifies if the authentication is successful.
+    /// </summary>
+    public bool IsSuccessful { get; set; } = false;
+
+    /// <summary>
+    /// The error received in case of expiry or consent rejection
+    /// </summary>
+    public string? Error { get; set; }
+
+    /// <summary>
+    /// The error message received in case of expiry or consent rejection
+    /// </summary>
+    public string? ErrorMessage { get; set; }
+}
+
+public interface IAuth0CibaService
+{
+    /// <summary>
+    /// Initiates a Client-Initiated Backchannel Authentication (CIBA) flow.
+    /// </summary>
+    /// <param name="request">Contains the information required for initiating the CIBA request.</param>
+    Task<CibaInitiationDetails> InitiateAuthenticationAsync(CibaInitiationRequest request);
+
+    /// <summary>
+    /// Polls the token endpoint to check the status of a CIBA request and retrieve tokens upon completion.
+    /// </summary>
+    /// <param name="cibaInitiationDetails">The information required to poll for the CIBA status.</param>
+    /// <param name="cancellationToken"><see cref="CancellationToken"/></param>
+    /// <returns>Details about the CIBA completion status or the retrieved tokens.</returns>
+    Task<CibaCompletionDetails> PollForTokensAsync(CibaInitiationDetails cibaInitiationDetails, CancellationToken cancellationToken = default);
+}